CFDG is a simple programming language for generating pictures.
It is based on syntax invented by Chris Coyne.
You specify a program consising of drawing rules, and a start rule. You can have multiple (conflicting) rules.
When this happens, CFDG picks one randomly. Infinite loops are okay, as long as the shapes get infinitely small.
The full syntax is described here.

This version of CFDG is written in pure PHP, it's platform-independent and relatively fast.